【作者】 张浩；

【导师】 刘邻渭；

【作者基本信息】 西北农林科技大学 ， 食品科学， 2003， 硕士

【摘要】 本研究利用河南辉县水柿作为试验材料酿制柿子果酒，研究在柿子成熟过程中糖、可溶性单宁以及总酸等各种指标的变化，柿子果酒的最佳工艺条件的确定以及柿子果酒的稳定性研究。结果显示：在柿果成熟过程中，主要成分的含量随着果实的不断生长而表现出有规律的变化，固形物含量和糖的含量总体呈上升趋势，达到峰值以后趋于平稳；单宁含量呈逐渐减少趋势；蛋白质含量呈缓慢降低趋势；柿果中总酸含量较低，在成熟过程中变化不大，各果实之间有一定的差异。应选择充分成熟的柿果，以保证糖度，降低单宁含量，此时柿果硬度＞20×105Pa，表皮呈现品种特有的橙黄色，含糖量达15～17%。维持一定的硬度有助于运输中的稳定性和完整性。采后的水柿在常温下放置10～15d可自然脱涩，硬度下降至7～8×105Pa，此时水柿中单宁含量下降至0.18%，可以保证发酵的顺利启动，并降低果酒苦涩味。当采后的柿子果实在室温下（20℃）放置，硬度逐渐下降至2.5×105Pa，可溶性单宁含量降低至0.171%，其他指标没有明显变化。但当硬度下降至2～3×105Pa时，柿果极易破损，因此选择柿果微软，硬度大约为7～9×105Pa时破碎进行酿造为宜。此时柿果中单宁含量较低，发酵的引发较为容易。酿造过程中应提高酸度，添加足量的SO2，适当提高酵母的接种量，保证发酵的顺利启动。过高的酵母添加量会造成发酵过猛，使发酵温度的控制困难，还会造成果酒澄清困难和香气物质的损失，单宁在发酵过程中随着含糖量的降低而降低，适当延长前发酵的时间可以降低果酒中可溶性单宁的含量。工艺条件较为理想的是发酵温度18.5℃，糖度为200 g·L-1， pH值为4.0，酵母添加量为0.3 g·L-1。柿子果酒微生物稳定性较好，但存在蛋白质破败和色素不稳定现象。为提高果酒的澄清度，可通过明胶（0.25g·L-1）+单宁(0.125 g·L-1)复合处理，提高其稳定性，如果果酒中含单宁量过高可添加0.35 g·L-1聚乙烯吡咯烷酮（PVPP）处理。柿子果酒中含1 g·L-1左右的苹果酸，可能会发生苹果酸-乳酸发酵，因柿子果酒的酸度较低，应抑制苹果酸-乳酸发酵的进行，应在发酵工艺的各个阶段注意SO2的足量添加，保证酒中游离SO2的量在50 mg·L-1以上，以保证成品的生物稳定性。为提高果酒的适口性可配制成柿子利口酒，半干酒的最佳配方为：糖度为12 g·L-1,柠檬酸为0.3%，酒精度为15o。半甜酒中苦味、酸味较干酒中淡，这主要是因为酒中含糖量增加，掩盖了单宁的苦味，该组的最佳配酒方案是：糖度为30 g·L-1，柠檬酸为0.2%，酒精度为20o。更多还原

【Abstract】 This research, with the DiospyroskakiL．from HuiXian County, Henan Province as the experiment materials, is designed to study the index changes of sugar, soluble tannin and total acid in the maturing process of persimmon, the determination of the optimum processing conditions for persimmon wine producing, and the determination of the persimmon stability. The results show that: During the maturing of persimmon, the contents of its main components present regular changes with the fruit growing: The soluble content and sugar content go up gradually and remain stable when their peak values reached; The tannin content decreases mildly and so does the content of protein; The low total acid content shows no great change but with certain degree of differences among different fruits. The fruits matured enough with orange color and hardness greater than 20×105Pa should be selected so as to guarantee the sugar contents and low tannin contents, and also the stability and intactness in the transportation. The collected persimmon can be kept under normal temperature for 10～15d for natural deastringency, and decreases of hardness to 7～8×105Pa and tannin content to 0.18% respectively, which can start the ferment smoothly and mild the bitter and astringent taste of the wine. During the brewing process, the acidity should be raised with adding sufficient SO2. The inoculation quantity of the yeast can be raised properly for the starting of the ferment. Over addition of yeast would make the ferment too fast which will add the difficulty of temperature control and the clarification of the wine, and the loss of aroma as well. The tannin content will be lowered during the ferment process with the decrease of the sugar content. If the time before the ferment properly be longered, the content of soluble tannin of the wine can be lowered. The optimum processing condition would be ferment temperature of 18.5℃,sugar content of 200 g·L-1, pH value of 4.0, and yeast addition of 0.3 g·L-1.The microbe in persimmon wine appears in a comparatively good stable state but the protein disease and polyphenol do not. In order to obtain a better clarification, the wine can be treated with gelatin（0.25g·L-1）and tannin (0.125 g·L-1) to improve its stability; while if the tannin content is too high, the wine can be treated by adding 0.35 g·L-1PVPP. <WP=9>About 1 g·L-1 of malic acid is contained in the wine, which may lead to malic acid and malolactic fermentation. Because of the low acidity in the persimmon wine, the fermentation should be restrained, and the sufficient amount of SO2 should be added in all the stages of the fermentation process in order to keep the free SO2 above 50 mg·L-1 for the biological stability of the wine. Persimmon liqueur can be produced to better its taste and the optimum direction for semi-dry persimmon wine is 12 g·L-1 of sugar, 0.3% of citric acid and 15o of alcohol contents. The bitterness and sourness of semi-sweet are light compared with that of dry wine, because its sugar content is raised which covers up the bitterness of the tannin. The optimum direction of it is 30 g·L-1 of sugar, 0.2% of citric acid and 20o of alcohol contents.更多还原